1. Field of the Invention
The present invention relates to a donor sheet, a method of manufacturing the same, a method of manufacturing a flexible thin film transistor (TFT) using the donor sheet where the active layers are made out of nanoparticles, and a method of manufacturing a flat panel display device using the donor sheet, and more particularly, to a donor sheet in which nanoparticles are arranged to be parallel to one another, a method of manufacturing the same, a method of manufacturing a thin film transistor (TFT) using the donor sheet, and a method of manufacturing a flat panel display device using the donor sheet.
2. Description of the Related Art
A flat panel display device such as a liquid crystal display (LCD), an organic light-emitting diode (OLED) display, or an inorganic light-emitting diode display are categorized by driving methods into a passive matrix (PM) flat panel display device using a passive driving method and an active matrix (AM) flat panel display device using an active driving method.
In the PM flat panel display device, anodes and cathodes, respectively, are arranged in a plurality of columns and rows, and a scanning signal is supplied by a row driving circuit to the cathodes. In this case, only one row of the plurality of rows is selected. In addition, a data signal is input by a column driving circuit into each pixel. The AM flat panel display device is widely used as a display device, which controls a signal input into each pixel using a thin film transistor (TFT) and is able to process an enormous amount of signals to realize a moving image.
TFTs of the AM flat panel display device include a semiconductor active layer having source/drain regions doped with high-concentration impurities and a channel region formed between the source/drain regions, gate electrodes insulated from the semiconductor active layer and placed in a region corresponding to the channel region, and source/drain electrodes each contacting each of the source/drain regions.
The semiconductor active layer is generally formed of amorphous silicon or polycrystalline silicon. Amorphous silicon can be deposited at a low temperature. However, when the semiconductor active layer is formed of amorphous silicon, electrical characteristics and reliability are lowered, and the region of a display device cannot be easily increased. In these days, polycrystalline silicon is widely used in forming the semiconductor active layer. Polycrystalline silicon has high current movement of several tens to hundreds cm2/V•s and low radio frequency operating characteristics and a low leakage current value and thus is very suitable for use in a high definition and large-sized flat panel display device.
However, when the semiconductor active layer is formed of polycrystalline silicon, a crystallization process of crystallizing amorphous silicon into polycrystalline silicon needs to be carried out. This involves heating to a high-temperature of 300° C. or higher.
Preferably, flat panel display devices should be able to bend to some degree by applying a predetermined tension thereto, allowing for a sufficient view angle, or so that the display can be used in a portable product such as an arm band, a wallet, or a notebook computer. However, when a TFT is formed of polycrystalline silicon using a conventional method, it is difficult to acquire a flexible flat panel display device. In other words, in order to process a flexible product, flexible materials such as acryl, polyimide, polycarbonate, polyester, mylar, and other plastic materials, should be used in most elements including the substrate. These plastic materials have low heat resistance, and if present when polycrystalline is formed, these materials will not tolerate the heat well. Thus, in order to process TFTs of the flat panel display device used in the flexible product, a method to form a structure at a temperature in which the plastic materials can withstand is needed.